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st: Data Setup for Survival Analysis With Unequal Interval


From   TA Stat <tastat@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   st: Data Setup for Survival Analysis With Unequal Interval
Date   Tue, 10 May 2011 21:58:32 +0700

Dear All

I would like to know the best way to run survival analysis (Cox PH
Model) in Stata (I am not sure I did it correctly) in a long format.
I also have a few points to discuss.

1.  The data is in a long format.  One row represents one hospital
visit.  Each visit we measured blood pressure and other lab tests
which will be time-varying covariates in Cox PH model.  However, the
time interval between hospital visits is not the same for each
patient.  Can Stata handle this?  I can calculate the numbers of days
or months from the first visit.  But I am not sure if I have to setup
the data in such a format that each visit is one or two months apart
for all patients.

2.  For the last visit, if the patient passed away, that patient won't
have a value of any time-varying covariates, would this effect the
analysis?  I am thinking about using missing data calculation to fill
in those values, but it doesn't make sense to me because the day that
patient passed away, those value such as systolic blood pressure
should be lower or higher than their normal level.

Thanks
Peter

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